This is a Continuation of Application No. PCT/JP99/03070 filed Jun. 9, 1999. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to an exposure method and an apparatus for transferring a mask pattern onto a photosensitive substrate in the lithography step for producing, for example, semiconductor devices, image pickup devices (for example, CCD), liquid crystal display devices, or thin film magnetic heads. In particular, the present invention is preferably used for a scanning type exposure apparatus based on, for example, the so-called step-and-scan system for transferring a mask pattern onto a substrate by synchronously moving a mask and the substrate with respect to a projection optical system.
2. Description of the Related Art
For example, when a semiconductor device is produced, a projection exposure apparatus is used, in which an image of a pattern on a reticle as a mask is transferred to respective shot areas on a wafer (or a glass plate or the like) as a substrate applied with a resist. Conventionally, a projection exposure apparatus (stepper) of the full field exposure type (static exposure type) has been frequently used as the projection exposure apparatus. Recently, the attention is also attracted by a scanning exposure type projection exposure apparatus (scanning type exposure apparatus) such as those based on the step-and-scan system in which a reticle and a wafer are subjected to scanning in a synchronized manner with respect to a projection optical system.
In general, in the case of the projection exposure apparatus of the full field exposure type, if the vibration, which acts to incline the optical axis of the projection optical system, is generated by the driving reaction force caused, for example, when the wafer stage is subjected to stepping movement, the relative positional relationship between the reticle and the wafer is changed by the vibration during the exposure. As a result, for example, it is feared that any overlay error occurs. For this reason, the conventional projection exposure apparatus is designed as follows as described in Japanese Patent Application Laid-Open No. 5-136023. That is, a sensor for detecting the vibration is arranged, for example, for the reticle stage and the wafer stage, and the exposure is stopped until the vibration disappears, for example, on the basis of the vibration information fed from the sensor. Alternatively, the positional discrepancy amount between the reticle and the wafer is postulated from the detected amount of vibration. The driving is controlled, for example, for the reticle stage on the basis of the result of the postulation. By doing so, it is intended that the relative positional relationship between the reticle and the wafer is not changed during the exposure.
In the case of the conventional full field exposure type projection exposure apparatus, it is enough that the movement stroke of the reticle stage is short. Therefore, a laser interferometer based on the double-pass system, which radiates the measuring laser beam from a main interferometer body to a corner cube to serve as a movement mirror in two directions perpendicular to one another, has been used to detect the position of the reticle stage. When the corner cube is used as the movement mirror, the laser beam, which comes into the corner cube, returns along an optical path which is parallel to the incoming direction. Therefore, even when the reticle stage is rotated in a minute amount, the laser beam, which is returned from the corner cube, is not greatly deviated from the laser beam which is returned from the reference mirror fixed, for example, to the projection optical system. Therefore, an advantage is obtained such that the position of the reticle stage can be detected highly accurately.
As described above, in the case of the conventional projection exposure apparatus of the full field exposure type, the exposure is stopped until the vibration disappears on the basis of the vibration information fed from the sensor provided, for example, for the stage, or the positional discrepancy amount between the reticle and the wafer is corrected by means of the postulation control depending on the detected amount of the vibration. Thus, the influence of the driving reaction force of the wafer stage or the like is reduced. However, in the case of the scanning type exposure apparatus based on the step-and-scan system or the like, the exposure is performed while moving the reticle stage and the wafer stage. Therefore, it is impossible to stop the exposure until the vibration disappears. Further, it is difficult to perform the exposure while postulating the positional discrepancy amount between the reticle and the wafer from the amount of vibration.
In the case of the scanning type exposure apparatus, the reticle stage is moved over a wide range (approximately corresponding, for example, to the width of the reticle in the scanning direction) in the scanning direction. Therefore, it is impossible to use the corner cube for the movement mirror for measuring the position of the reticle stage in the non-scanning direction perpendicular to the scanning direction. In place of the corner cube, it is necessary to use a plane mirror having a length equivalent to the movement range of the reticle stage. In this case, if the distance between the plane mirror (movement mirror) and the reference mirror is long, for example, even when the laser interferometer based on the double-pass system is used, the laser beam, which is returned from the plane mirror, is deviated relatively greatly, when the reticle stage is rotate in a minute amount. It is feared that the position of the reticle stage cannot be detected. For this reason, in the case of the conventional scanning type exposure apparatus, in order to arrange the movement mirror and the reference mirror closely to one another, the reference mirror has been arranged on a reticle support stand in the vicinity of the movement mirror. In this arrangement, the vibration of the projection optical system is not directly reflected to the measured value of the laser interferometer. Therefore, an inconvenience arises such that it is impossible to highly accurately measure the relative positional relationship of the reticle on the basis of the projection optical system if the vibration is large.
In the case of the projection exposure apparatus of the full field exposure type, it is also necessary to use the plane mirror as the movement mirror when a structure, in which the movement amount of the reticle stage is large, is used. Therefore, the same inconvenience as described above arises.
Taking the foregoing points into consideration, a first object of the present invention is to provide an exposure apparatus and an exposure method which make it possible to highly accurately detect the relative positional relationship between the reticle stage and the projection optical system so that the reticle and the wafer may be subjected to highly accurate positional alignment, even when the movement range of the reticle stage is wide. A second object of the present invention is to provide an exposure apparatus and an exposure method which make it possible to reduce the influence of the driving reaction force of the reticle stage or the wafer stage on the positioning accuracy so that the exposure may be performed highly accurately.
Still another object of the present invention is to provide a method for producing the exposure apparatus as described above, and a method for producing a device, which makes it possible to produce the highly accurate device by using the exposure apparatus as described above.
A first exposure apparatus according to the present invention is an exposure apparatus for exposing a substrate (W) with an image of a pattern on a mask (R); comprising a projection optical system (5) which is arranged between the mask (R) and the substrate (W) and which projects the image of the pattern onto the substrate (W); a mask stage (9, 11) which holds and moves the mask (R); a mask base (14) which supports the mask stage (9, 11); and an interferometer (43X) which radiates a measuring light beam (LXM) onto the mask stage (9, 11) and radiates a reference light beam (LXR) onto a reference mirror (22X) arranged in the vicinity of the projection optical system (5) to detect a position of the mask stage (9, 11) on the basis of an interference light of the measuring light beam and the reference light beam; wherein a radiation position of the measuring light beam (LXM) on the mask stage (9, 11) is set to be deviated toward the projection optical system (5) with respect to a plane (14a) of the mask base on which the mask stage (9, 11) is moved.
According to the first exposure apparatus of the present invention as described above, the radiation position of the measuring light beam (for example, a movement mirror or a mirror surface) is set to be deviated toward the projection optical system with respect to the plane on which the mask stage (9, 11) is moved. Therefore, even when the reference mirror is arranged in the vicinity of the projection optical system (for example, on the upper side surface of a body tube of the projection optical system), the radiation position can be arranged closely to the reference mirror. Therefore, even when the projection optical system is displaced in a minute amount, or even when the mask stage is rotated in a minute amount, then it is possible to highly accurately detect the relative positional relationship between the mask stage and the projection optical system. Consequently, the mask and the substrate can be subjected to highly accurate positional adjustment.
It is desirable that the exposure apparatus is an exposure apparatus of a scanning exposure type, and the interferometer (43X) is an interferometer which measures the position of the mask stage in a non-scanning direction perpendicular to a scanning direction.
It is desirable that the exposure apparatus further comprises a support member (15) which supports the mask base (14) and the projection optical system (5). It is desirable that the support member (15) supports the interferometer (43X).
It is desirable that the mask base (14) has an opening for projecting the pattern, and at least a part of the projection optical system (5) is located at the inside of the opening.
In another aspect, a second exposure apparatus according to the present invention is an exposure apparatus for exposing a substrate (W) with an image of a pattern on mask (R) via a projection optical system (5); comprising a mask stage (9, 11) which is supported movably with respect to a base member (14) and which is movable in a predetermined direction while holding the mask (R); a mask side reaction force-reducing member (13) which is supported movably with respect to the base member (14) at the outside of the mask stage (9, 11) and which is movable to offset any reaction force generated when the mask stage (9, 11) is driven; and a driving member (12) which is arranged between the mask stage (9, 11) and the mask side reaction force-reducing member (13) and which drives the mask stage (9, 11); wherein the mask stage (9, 11) includes a first stage member (11) which is movable in a predetermined direction; and a second stage member (9) which is movable in the predetermined direction together with the first stage member (11) while holding the mask (R) and which is finely movable with respect to the first stage member (11) in a plane parallel to a plane (14a) of the base member (14) on which the mask stage (9, 11) is moved, so that a position of the mask (R) is adjusted.
According to the second exposure apparatus of the present invention as described above, when the mask stage is driven in the predetermined direction by the aid of the driving member (12), for example, the mask side reaction force-reducing member (13) is moved in the opposite direction in accordance with the law of action and reaction. The movement of the center of gravity almost disappears as a whole, and no vibration is caused. Therefore, it is possible to reduce the influence of the driving reaction force of the mask stage, for example, on the positioning accuracy, and it is possible to perform the exposure highly accurately.
The mask stage and the mask side reaction force-reducing member are supported by the common base member. Accordingly, the mask side reaction force-reducing member can be installed to the exposure apparatus without increasing the distance between the mask and the projection optical system. Therefore, the mask side reaction force-reducing member can be installed with ease even for an exposure apparatus in which at least one width of the illumination area is large, and the distance between the mask and the projection optical system (working distance on the mask side) is short.
The position of the mask can be also adjusted during the movement of the mask by finely driving the second stage member (9) with respect to the first stage member (11). For example, when the scanning exposure is performed, it is possible to highly accurately correct the synchronization error between the mask and the substrate.
It is desirable that a mass of the mask side reaction force-reducing member (13) is not less than five times a mass of the mask stage (9, 11).
In still another aspect, a third exposure apparatus according to the present invention is an exposure apparatus for exposing a substrate (W) with an image of a predetermined pattern via a projection optical system (5); comprising a substrate stage (3) which holds and moves the substrate (W); and a substrate side reaction force-reducing member (2) which is supported movably with respect to a base member (30), which movably supports the substrate stage (3), and which is movable to offset any reaction force generated when the substrate stage (3) is driven; wherein a mass of the substrate side reaction force-reducing member (2) is not less than five times a mass of the substrate stage (3).
According to the third exposure apparatus of the present invention as described above, for example, when the substrate stage is driven by the driving member between the substrate side reaction force-reducing member (2) and the substrate stage (3), for example, the substrate side reaction force-reducing member is moved in the opposite direction in accordance with the law of action and reaction. Therefore, the movement of the center of gravity almost disappears as a whole, and hence it is possible to reduce the influence of the driving reaction force of the substrate stage, for example, on the positioning accuracy.
Further, it is possible to reduce the influence of the driving reaction force on the exposure apparatus during the driving of the stage system without increasing the foot print (installation area) even for the stage system which is moved over a range that is wide in the two-dimensional direction as in the substrate stage by movably supporting the substrate stage, for example, on the substrate side reaction force-reducing member and movably supporting the substrate side-reaction force-reducing member on the base member.
Further, the mass of the substrate side reaction force-reducing member is not less than five times the mass of the substrate stage. Therefore, the following advantage is obtained. That is, it is easy to increase the relative velocity of the substrate stage with respect to the base member, and it is possible to decrease the driving amount of the substrate side reaction force-reducing member.
It is desirable that the exposure apparatus further comprises a support member (15) which supports the base member (30) and the projection optical system (5).
In still another aspect, a fourth exposure apparatus according to the present invention is an exposure apparatus for exposing a substrate (W) with an image of a pattern on a mask (R); comprising a projection optical system (5) which is arranged between the mask (R) and the substrate (W) and which projects the image of the pattern onto the substrate (W); a mask stage (9, 11) which is movable while holding the mask (R); and a mask base (14) which movably supports the mask stage (9, 11) and which is provided with an opening for projecting the image of the pattern; wherein the mask stage (9, 11) holds the mask (R) so that a pattern plane of the mask (R) is located at a position deviated toward the projection optical system (5) with respect to a plane (14a) of the mask base (14) on which the mask stage (9, 11) is moved, and at least a part of the projection optical system (5) is located at the inside of the opening.
According to the fourth exposure apparatus of the present invention as described above, the pattern plane of the mask (R) is located at the position deviated toward the projection optical system (5) with respect to the plane of the mask base (14) on which the mask stage (9, 11) is moved. Therefore, the mask (R) and the projection optical system (5) can be arranged closely to one another, and the working distance on the side of the mask (R) can be designed to be short. Further, the portion of the mask stage (9, 11) for holding the mask (R) is located at the position deviated toward the projection optical system (5) with respect to the plane (14a) on which the mask stage is moved. Therefore, when a movement mirror for detecting the position of the mask stage (9, 11) is installed at the portion for holding the mask (R), it is easy to realize the first exposure apparatus of the present invention.
It is desirable that the exposure apparatus further comprises a movement unit which is movably supported by the mask base (14) and which is movable in an opposite direction with respect to the mask stage (9, 11).
In still another aspect, a first exposure method according to the present invention is an exposure method for exposing a substrate (W) with an image of a pattern on a mask (R) via a projection optical system (5) arranged between the mask (R) and the substrate (W), the exposure method comprising using a mask stage (9, 11) including a first stage (11) which is movable in a predetermined direction and a second stage (9) which is movable together with the first stage (11) while holding the mask (R); radiating a measuring light beam (LXM) onto a position deviated toward the projection optical system (5) from a plane (14a) of a mask base (14) which supports the mask stage (9, 11) and on which the mask stage (9, 11) is moved; and radiating a reference light beam (LXR) to a reference mirror (22X) arranged in the vicinity of the projection optical system (5) so that a position of the mask stage (9, 11) is detected on the basis of an interference light of the measuring light beam and the reference light beam.
According to the first exposure method of the present invention as described above, it is possible to highly accurately detect the positional relationship between the mask stage and the projection optical system. Consequently, it is possible to effect the highly accurate positional adjustment for the mask and the substrate.
In still another aspect, a second exposure method according to the present invention is an exposure method for exposing a substrate (W) with an image of a pattern on a mask (R) via a projection optical system (5); comprising moving a mask stage (9, 11) including a first stage member (11) which is supported movably with respect to a base member and a second stage member (9) which is movable together with the first stage member (11) which holds the mask (R), while moving a mask side reaction force-reducing member (13), which is supported movably with respect to the base member (14) and which is arranged at the outside of the first stage member (11), to offset any driving reaction force of the mask stage (9, 11); and finely moving the second stage member (9) with respect to the first stage member (11) in a plane which is parallel to a plane (14a) of the base member (14) on which the mask stage (9, 11) is moved so that a position of the mask (R) is adjusted.
According to the second exposure method of the present invention as described above, no vibration is caused when the mask stage is driven in a predetermined direction. Therefore, it is possible to reduce the influence of the driving reaction force of the mask stage, for example, on the positioning accuracy. Thus, it is possible to perform the exposure highly accurately.
The position of the mask can be also adjusted during the movement of the mask (R) by finely driving the second stage member (9) with respect to the first stage member (11).
In still another aspect, a third exposure method according to the present invention is an exposure method for exposing a substrate (W) with an image of a predetermined pattern via a projection optical system (5); comprising driving a substrate stage (3) which holds and moves the substrate (W), wherein a substrate side reaction force-reducing member (2), which has a mass of not less than five times that of the substrate stage (3), which is supported movably with respect to a base member (30), and which movably supports the substrate stage (3), is moved to offset any driving reaction force of the substrate stage (3).
According to the third exposure method of the present invention as described above, the center of gravity is scarcely moved as a whole. Therefore, it is possible to reduce the influence of the driving reaction force of the substrate stage, for example, on the positioning accuracy. Further, it is possible to reduce the influence of the driving reaction force on the exposure apparatus when the stage system is driven, without increasing the foot print (installation area), even in the case of the stage system such as the substrate stage which is moved over a wide range in two-dimensional directions. Further, it is easy to increase the relative velocity of the substrate stage with respect to the base member, and it is advantageous to decrease the driving amount of the substrate side reaction force-reducing member.
In still another aspect, a fourth exposure method according to the present invention is an exposure method for exposing a substrate (W) with an image of a pattern on a mask (R) via a projection optical system (5) arranged between the mask (R) held on a movable mask stage (9,11) and the substrate (W); the exposure method comprising locating a pattern plane of the mask (R) at a position deviated toward the projection optical system (5) from a plane (14a) of a mask base (14) which supports a mask stage (9, 11) and on which the mask stage (9, 11) is moved, wherein at least a part of the projection optical system (5) is disposed in an opening formed in the mask base (14).
According to the fourth exposure method of the present invention as described above, the pattern plane of the mask (R) is located at the position deviated toward the projection optical system (5) from the plane of the mask base (14) on which the mask stage (9, 11) is moved. Therefore, the mask (R) and the projection optical system (5) can be arranged closely to one another. It is possible to design the working distance on the side of the mask (R) to be short.
In still another aspect, a first method for producing an exposure apparatus according to the present invention is a method for producing an exposure apparatus for exposing a substrate (W) with a pattern on a mask (R) via a projection optical system (5), the method comprising assembling the following components in a predetermined positional relationship, i.e., a mask stage (9, 11) including a first stage (11) which is movable in a predetermined direction and a second stage (9) which is movable together with the first stage (11) while holding the mask (R); a mask base (14) which supports the mask stage (9, 11); and an interferometer (43X) which radiates, for the mask stage (9, 11), a measuring light beam (LXM) onto a position deviated toward the projection optical system (5) from a plane (14a) of the mask base (14) on which the mask stage (9, 11) is moved, and which radiates a reference light beam (LXR) onto a reference mirror (22X) arranged in the vicinity of the projection optical system (5) so that a position of the mask stage (9, 11) is detected on the basis of an interference light of the measuring light beam and the reference light beam.
In still another aspect, a second method for producing an exposure apparatus according to the present invention is a method for producing an exposure apparatus for exposing a substrate (W) with an image of a pattern on a mask (R) via a projection optical system (5), the method comprising assembling the following components in a predetermined positional relationship, i.e., a mask stage (9, 11) including a first stage member (11) which is movable in a predetermined direction and a second stage member (9) which is movable in the predetermined direction together with the first stage member (11) while holding the mask (R) and which is finely movable with respect to the first stage member (11) in a plane parallel to a plane (14a) on which the first stage member (11) is moved to adjust a position of the mask (R); a mask side reaction force-reducing member (13) which is movable to offset any reaction force generated when the mask stage (9, 11) is driven, at the outside of the mask stage (9, 11); and a driving member which is arranged between the mask stage (9, 11) and the mask side reaction force-reducing member (13) and which drives the mask stage (9, 11).
In still another aspect, a third method for producing an exposure apparatus according to the present invention is a method for producing an exposure apparatus for exposing a substrate (W) with an image of a predetermined pattern via a projection optical system (5), the method comprising assembling the following components in a predetermined positional relationship, i.e., a substrate stage (3) which holds and moves the substrate (W); and a substrate side reaction force-reducing member (2) which has a mass of not less than five times that of the substrate stage (3), which is supported movably with respect to a base member (30), which movably supports the substrate stage (3), and which is movable to offset any reaction force generated when the substrate stage (3) is driven.
In still another aspect, a fourth method for producing an exposure apparatus according to the present invention is a method for producing an exposure apparatus for exposing a substrate (W) with an image of a pattern on a mask (R), the method comprising arranging a projection optical system (5) at such a position between the mask and the substrate as to project the image of the pattern onto the substrate (W); arranging a base member (14) which has a predetermined movement plane (14); and arranging a mask stage (9, 11) including a first stage (11) which is movable in a predetermined direction and a second stage (9) which is movable together with the first stage (11) while holding the mask (R) so that a pattern plane of the mask (R) is located at a position deviated toward the projection optical system (5) from the movement plane (14a).
In still another aspect, a method for producing a device according to the present invention is a method for producing a predetermined device, comprising the step of transferring, by exposure, a pattern onto a substrate (W) by using the exposure apparatus of the present invention. According to the method for producing the device of the present invention as described above, the mask and the substrate are subjected to the highly accurate positional adjustment by using the exposure apparatus of the present invention. As a result, it is possible to obtain the high performance device.